Excessive phosphorus (P) in surface waters causes eutrophication thereby resulting in excessive plant growth, fish kills, poor drinking water quality, and overall decrease in environmental quality/recreation. Potential sources of phosphorus to surface waters include waste-water treatment plants, horticultural operations, and runoff from agricultural and urban/suburban land, including golf courses.
Soils become saturated with phosphorus through continuous over application of phosphorus to growing plants. The soils with high levels of phosphorus then slowly release dissolved phosphorus in runoff. There are currently no effective best management practices (BMPs) for reducing transport of dissolved phosphorus. Most BMPs only prevent erosion, which will only reduce particulate phosphorus transport, not dissolved phosphorus. Even if all phosphorus applications to high phosphorus soils are stopped, it will require at least 15 years for soil phosphorus concentrations to decrease to acceptable levels if plants are harvested from the site. In the meantime, these soils will release dissolved phosphorus during every runoff event. Dissolved phosphorus presents a greater and more immediate problem compared to particulate phosphorus (i.e. phosphorus adsorbed onto soil particles) because dissolved phosphorus is 100% bio-available to aquatic organisms. In regard to runoff, dissolved phosphorus is a difficult form to control since particulate losses are typically controlled by maintaining sufficient soil cover and reducing erosion. Dissolved phosphorus loads in runoff are greatest from soils that are high in soil test phosphorus and soils with recent surface applications of phosphorus.
A possible solution to the problem of excess phosphorous is the application of phosphorus sorbing materials to affected soils. Such materials can be applied directly to the soil or included with applied animal manures. These techniques have been shown to reduce dissolved phosphorus transport in runoff during rainfall events. However, phosphorus sorbed onto these materials may become soluble again with time, or due to changes in chemical conditions. Therefore, phosphorus is not truly removed from the system, only temporarily made insoluble.
Another potential solution is direct application of phosphorus sorbing materials to surface waters (lakes, ponds, etc.). This has been shown to be effective for reducing soluble phosphorus concentrations in the water column of various lakes. However, this approach only reduces the solubility of phosphorus in the system; phosphorus is not actually removed from the water. The sorbed phosphorus can be re-dissolved with time, or upon changes in chemical conditions.
What is needed is a system and method for addressing the above, and related, issues.